CH615806A5 - Device for dispersing a vaporisable substance and use of the device - Google Patents

Abstract

A device for dispersing, at a predetermined rate, a vaporisable substance by diffusion of the vapour across a stagnant gas layer. The device comprises at least one long conduit (2) designed for a vaporisable substance (8), of predetermined cross-sectional surface area and length, which is closed at one end and which consists of a material chosen from polyesters, polyolefins, acrylic polymers and polyamides. The stagnant gas layer covers the vaporisable substance in the conduit. The device is suitable for the release, at controlled rate, of vapours such as insect attractants, insecticides and other vapours such as flower perfumes. <IMAGE>

Description

The present invention relates to a device for the dissemination of a vaporizable substance at a predetermined speed by diffusion of the vapor through a layer of stagnant gas, and to a use of the device.

It mainly relates to insecticide control; nevertheless, its concepts can be applied to all cases of controlled dissemination of a vapor. However, since substances which attract insects are of great importance, the description of the present invention will focus on such use.

The fact that insects can be attracted or repelled by certain substances has been known for many years. For some time, efforts have been made to exploit this ancient knowledge and to extend it to disinsectization and to the mitigation of the harmful effects that insects can exert on humans, animals, crops, textiles. , etc. We have thus been led to recognize that olfaction plays a preponderant role in communication between insects and that the means of communication are chemical substances produced and emitted by insects for communication purposes. These chemical messengers have been called pheromones and are known to have great specificity in insects, both in terms of the species and the response to them. Pheromones can serve as alarm signals, aids for food discovery, signals for mating, trail marking substances, or defensive substances to ward off predators.

Numerous pheromones that exert sexual attraction in insects have been isolated and identified with regard to their chemical composition and structure. These are typically straight or cyclic chain organic compounds formed of carbon, hydrogen and oxygen, whose molecular weight is between 150 and 130. The structure and biological activity of most known sex pheromones in insects are reviewed in the book entitled “Insect Sex Pheromones” by Martin Jacobson, Academic Press, New York, 1972. Among the sex pheromones identified, many were able to be obtained by synthesis and synthetic substances could be used in various ways to aid in the control of parasitic insects.

The insect sex pheromones have been used in two general ways. One involves using the pheromone to lure a target insect to a trap or to a point where it can be destroyed by an insecticide. Trapping also serves as a means of studying the application of chemical insecticides over time. A second method involves the dissemination of small point sources of pheromone in an infested area to disorient the insects and make it difficult or even impossible to bring the opposite sexes together. This latter process is called the disruptive technique, and is intended to suppress the population of parasitic insects by destroying or interrupting the natural process of mating and reproduction.

The effective and cost-effective use of insect sex pheromones to achieve pest control, regardless of the strategic method, requires a suitable means of dissemination. A dissemination process or device must release the pheromone into the atmosphere at a specific speed specific to the target insect, and regardless of the period of sexual activity of particular adult insects. Since synthetic sex pheromones are often quite expensive materials, the means or devices of dissemination must be as effective as possible in the use of the pheromone. Thus, one must use a practical and economical system of sustained release to disseminate the pheromone, a system which allows the release of the attractive substance at a speed and for a well-defined period.

Many examples of sustained or controlled release systems exist in the known field of insecticide control. U.S. Patents Nos. 2956073, 3116201 and 3318769 teach the manufacture and use of insecticides formulated into plastic articles of a given shape, which release the insecticide at a prescribed rate for an extended period of time. U.S. Patent No. 3,539,465 teaches microencapsulation of emulsions of a hydrophilic liquid in oil, the polymeric encapsulation walls of which allow the limited release of encapsulated substances such as insecticides and d other biocidal agents. U.S. Patent No. 3,740,419 teaches the use of insecticide-impregnated wood shavings as a device for destroying slow-release pests. U.S. Patent No. 3,577,515 teaches the manufacture of microencapsulated insecticidal compositions by an interfacial polymerization process to form a porous encapsulating wall which limits the rate of release of the insecticide. U.S. Patent No. 3,590,118 describes a slow release insect repellant system in the form of an acrylic film acting on the respiratory tract. U.S. Patent No. 3,592,910 describes the use of insecticide formulations based on terpene resin, intended to prolong the period of effectiveness of non-persistent or moderately persistent insecticides.

Each of these methods has its own quota of advantages and disadvantages, which need not be discussed in the present specification. It is more important to mention that researchers, especially in the field of applied entomology, continue to seek a more satisfactory means for the uniform, quantitatively predictable and prolonged automatic dissemination of tiny quantities of substances.

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volatiles active at an extremely slow limited speed. Sometimes spread is desired from one tree to another, as is the case, for example, in the fight against certain pests in orchards. At other times, the spread must be uniform and cover large areas, such as when pheromones are used to disrupt mating signals from parasitic insects attacking crops. These objectives can be achieved with good results by using fine capillary tubes, both as containers and as distribution means.

Several researchers have obtained more or less limited success in using microscopic tubes or capillaries in laboratory tests and under limited experimental conditions, in the field. Various other major obstacles have been encountered, as have other researchers in the field, when it comes to extending the practical application of the classical forms of these devices. However, we have also discovered a new and effective variant of the method and of the dissemination device using microscopic tubes, a variant which succeeds in overcoming these obstacles and which makes it possible very advantageously to use thinner tubes for the purpose sought in practical applications.

The first users of microscopic tubes for the dissemination of pheromones regularly used these tubes as containers and distributors, with both ends open to the atmosphere. The rate at which the pheromone is discharged from the ends of microscopic tubes or capillaries, when used in this way, has generally been too high for most practical field applications. In addition, when open at the ends, these devices suffer great losses of material due to mechanical shocks, vibrations, wind, etc.

The invention, which uses tubes closed at one end, eliminates, although it is excessively simple, several important obstacles opposing the use of these devices and gives them practical interest to an extent which has not still could have been considered by specialists in this field.

By way of example illustrating the prior art, reference is made to the article entitled “Novel Trapping and Delivery Systems for Airborne Insect Pheromones” by Lloyd E. Browne et al., Published in “J. Insect Physiol. ”, 1974, vol. 20, pp. 183-193. This article describes (pp. 187-188) a laboratory test device which makes it possible to test the effectiveness of pheromones, the active liquid being introduced into a capillary glass tube of 5 ni neither placed vertically and open at both ends. The liquid contained in this tube evaporates continuously at the liquid-air interface exposed at the base of the capillary tube, where it continuously arrives by gravity. Although the speed of dissemination can be kept fairly constant, it is also quite high, of the order of 1 nl / min. The capillary tube is approximately 5 cm long and 0.4 mm in diameter. A total charge of hexane is disseminated in approximately 5 min in the test described.

Another example of a prior process using microscopic tubes is described by Shorey et al in "Sex Pheromones of Lepidoptera. XXX. Disruption of Sex Pheromone Communications in "Trichoplasia ni" as a Possible Means of Mating Control "," Environmental Entomology ", vol. 1, N ° 5, October 1972, pp. 641-645. Pheromone evaporation systems at low, intermediate and high speeds are described in this article. It should be noted that, in this work, the authors contemplate the use of microscopic tubes as part of the technique of high speed dissemination.

The substrates used for high evaporation rates were based on the principle of exposure to air of a liquid film of the pure chemical agent. The speed was varied by changing the air of the exposed film. Such evaporators could have been left in the open air for several days without their rate of release of the substance decreasing. In practice, however, they have been maintained and recharged daily. The evapo-

The flow generator at 10 ng / min consisted of a Teflon tube with an internal diameter of 0.38 mm and a length of 20 mm, arranged vertically in a clamp attached to a wooden stake. Looplure was retained in the lower end of the tube by capillary action. An aluminum weighing pan attached upside down to the top of the stake was used to protect the tube from excessive winds, which sometimes drove the Looplure from unprotected tubes. The 30 ng / min evaporator consisted of three similar Teflon tubes held in one clamp.

The principle of the dissemination is the same in this system as above: the liquid evaporates continuously at the liquid-air interface maintained by gravity at the bottom of a vertical capillary tube open at both ends. The particular rates of dissemination of these materials are at least ten times greater and can be up to 1000 times greater than that which can be obtained using the present invention. It should also be noted that, due to the configuration open at both ends, the contents of the tubes are retained in an unstable manner and risk being blown away by the wind. It is important to note also the daily maintenance which is essential. The device of the invention overcomes these two drawbacks.

As another example illustrating the prior art, we can cite the article by Pitman and Vité entitled "Field Response of Dendrocto-nus Pseudosugae (Coleoptera: Scolytidae) to Synthetic Fron talin" published in "Annals of The Entomological Society of America ", vol. 63, N ° 3, pp. 661-664, May 1970; these authors use glass capillary tubes with an internal diameter of 0.4 mm for the dissemination of synthetic frontaline. The release rate they obtain is 5 mg / h. By operating according to the invention, with the same pheromone and a tube of roughly equivalent diameter, the speed is reduced by two to three orders of magnitude (that is to say from 100 to 1000 times). This shows the superiority of the practical implementation of the device of the invention for the long-term controlled dissemination of small quantities of this pheromone as well as others; the superiority is such that the principle of the invention can be extended to pesticide control on a large scale, in contrast to the limited experimental results obtained by the former researchers.

Consequently, the main object of the invention resides in an improved device for disseminating vapors intended for various applications, for example pheromones and perfume vapors, according to which the dissemination of vapor is regulated over time and its duration can be prolonged by evaporation of the substance to be evaporated, through a layer of stagnant gas as well as in a device of this type which can be loaded easily with a correct quantity of material to be vaporized.

The device according to the invention is characterized in that it comprises at least one elongated conduit, containing the vaporizable substance, which is closed at one end and which is constituted by a material chosen from polyesters, polyolefins, acrylic polymers and polyamides, and the stagnant gas layer covers the vaporizable substance in the conduit. The device of the type defined above disseminates vapor, in particular a pheromone, into the atmosphere at a specific speed specific to the target insect, and during any period of sexual activity of particular adult insects. In these devices, the system for disseminating the substance to be vaporized is effective in performing its function.

The invention makes possible the dissemination in an environment, at a regulated speed, of a vapor such as perfumes of flowers, fruits, wood, etc., for aesthetic purposes.

The invention also relates to a use of the device according to the invention for combating insects, which is characterized in that at least one tube contains a vaporizable insecticide.

The characteristics and advantages of the invention will emerge from the detailed description which follows.

To demonstrate the very good limited release capabilities of the system of the present invention, certain data have been

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taken from the prior art and are reproduced in part A of table I. Similar experiments conducted in parallel with the present invention and involving the use of microscopic polyethylene terephthalate tubes, open at both ends and disseminating one of the pheromones identified in part A, are presented in part B of table I. For comparison, results obtained in accordance with the invention are given in part C of table I.

Table I Comparative dissemination rates

Flow Tube

Area Diameter Per Standardized Tube

Source Substance to be evaporated (mm) (mm2) (mg / h) (mg / mm2 / h)

A Prior art - tubes open at both ends

1.

Browne, "J. Ins. Phys. "

hexane

0.4

0.125

60

480

2.

Shorey, "Approx. In t. "

looplure

0.38

0.125

0.0006

0.0048

3.

Pitman / Vité, Boyce,

Frontaline thompson

0.4

0.125

5

40

B

Test parallel to the present invention - tubes open to

two ends

1.

Frontaline vertical tubes

0.16

0.02

0.12

6

2.

Frontaline horizontal tubes

0.4

0.125

0.89

7.1

3.

Frontaline vertical tubes

0.4

0.125

1.3

10

VS

The invention

1.

frontaline

0.4

0.125

0.0068

0.054

2.

frontaline

0.16

0.02

0.0009

0.045

3.

CCU

0.2

0.03

0.018

0.6

4.

o-dichlorobenzene

0.2

0.03

0.002

0.066

5.

cis-7-dodecenyl acetate

0.2

0.03

0.000012

0.0004

6.

cis-8-dodecenyl acetate

0.16

0.02

0.000012

0.0005

7.

linalool

0.2

0.03

0.0003

0.010

8.

disappearance

0.2

0.03

0.00006

0.002

9.

grandlure

0.2

0.03

0.0003

0.010

It appears from part A of table I that the speed of dissemination of frontaline, reduced to the hollow transverse section of the fiber, is 40 mg / mm2 / h in the work of Pitman and Vité using glass capillary tubes 0.4 mm in diameter, held vertically. This result must be compared to that obtained in parallel with the invention using the same chemical compound in a 0.4 mm polyethylene terephthalate tube open at both ends and held vertically (Table I B). The difference between the values of 40 mg / mm2 / h and 10 mg / mm2 / h can be attributed to the fact that the Pitman and Vité method involves the use of an olfactometer with a limited speed of forced passage of air through the open end of the tube, while, in the experiment of the invention, evaporation is carried out in a laboratory in which the air is practically stagnant. Evaporation in both cases takes place at the air-liquid interface continuously presented at the base of the microscopic tubes. In the experiment of the invention, the same microscopic tube held horizontally gives a speed of dissemination of 7.1 mg / mm2 / h, a little lower than when the tube is held vertically. A smaller capillary tube (0.16 mm), held vertically, gives a slightly slower flow rate of 6 mg / mm2 / h, but still quite comparable to that obtained with the capillary of larger diameter. The important point to note is that all these tests give a dissemination rate of the same order of magnitude, that is to say of 10 mg / mm2 / h.

In contrast to the content of parts A and B of table I, part C of table I gives results concerning the prolonged and limited rate of dissemination which is obtained by the invention. The first two lines of part C of table I provide information on the dissemination of frontaline by two different diameters of microtubes. It should be noted that these two flow rates are completely consistent with each other, being equal to 0.054 and 0.045 mg / mm2 / h. These values differ by a factor of 200 x from the results given in part B of table I, and by a value reaching a factor of 1000 x from the results given in part A of this same table. Lines 3 and 4 of part C of table 45 give the evaporation rates obtained for two very common substances, namely carbon tetrachloride and orthodichlorobenzene, the first of high volatility and the other of moderate volatility. It should be noted that their release rates are in a ratio of 10: 1, which is quite consistent with their relative vapor pressures at room temperature. However, in contrast to the spread of hexane (line 1 of Table I A), with volatility comparable to that of carbon tetrachloride, they evaporate 1000 to 10000 times less quickly. The rest of part C of table I gives 55 rates of dissemination of several pheromones. Line 5 which corresponds to the dissemination of the looplure (cis-7-dodecenyl acetate) must be compared to Shorey's work illustrated in the second line of part A of table I. We note in part C that there are a reduction by a factor of 10 in the rate of dissemination by the invention. The results of line 6, concerning cis-8-dodecenyl acetate, are entirely consistent with the dissemination results obtained for the cis-7 isomer. The results of lines 7, 8 and 9 further confirm the advantages of the present invention.

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Table II gives the chemical names and the insects concerned, for several of the pheromones chosen for which results have been reproduced in Table I.

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Table II

Correlation between the common name, the chemical name and the target insect, for the substance to be evaporated from the table of comparative flows

(i.e. Table I)

Common name (substance to evaporate)

Chemical name

Insect targeted

Carbon tetrachloride o-Dichlorobenzene

Disparlure

Frontaline cis-8-dodecenyl acetate

Gandlure, compounds I-IV: Compound I Compound II Compound III Compound IV Hexane Linalool Looplure

T Etrachloromethane 1,2-Dichlorobenzene Cis-7,8-epoxy-2-methyloctadecane Cis-8-dodecenyl acetate 1,5-Dimethyl-6,8-dioxabicyclo- (3.2.1) octane

Cis-2-isopropenyl-1-methylcyclobutane-ethanol Cis-3,3-dimethyl-A1 'p-cyclohexane-ethanol Cis-3,3-dimethyl-A1'a-cyclohexane-ethanal T rans-3,3-dimethyl- A1, <z-cyclohexane-ethanal Hexane

3,7-Dimethyl-1,6-octadiene-3-ol Cis-7-dodecenyl acetate

Bombyx disparate Oriental budworm Scolyte du pin Cotton weevil

Cabbage looper

The invention relates to the elements and combinations of elements, the construction features and the assemblies which are described below and of which various possible embodiments are shown in the accompanying drawings, in which: FIG. 1 is a longitudinal section of a filiform tube illustrating the present invention, filled with a substance to be vaporized;

fig. 2 shows a group or a bundle of lined tubes 30 according to FIG. 1, mounted on a support in vertical position;

fig. 3a illustrates an assembly method on an adhesive support of a parallel continuous group of filled hollow fibers, having in places heat-sealed zones sealing off the tubes, and FIG. 3b illustrates how an individual dispenser can be cut from such tape;

fig. 4a illustrates an individual hollow fiber filled with substance to be evaporated, open at one end and closed on itself at the other end by fusion welding;

fig. 4b illustrates a hollow fiber of the same configuration, which has not been cut in the heat sealed part, but which consists of two microscopic conduits each having an open end and a closed end;

fig. 5 is a graphical representation of the variation in the rate of release of carbon tetrachloride in accordance with the invention, as a function of time, and corresponds to example 3 of part C of table I; the internal cross-sectional area of the fiber is 3.245 x 10 ~ 4 cm2; time is expressed in hours and weight loss is expressed in g / min x 107;

fig. 6 is a graph similar to that of FIG. 5, illustrating the release rate of o-dichlorobenzene in accordance with the invention, and corresponds to Example 4 of Part C of Table I; the cross-sectional area is 3.09 x 10 ~ 4 cm2;

fig. 7 is a graph illustrating the rate of release of the linalool in accordance with the invention and corresponds to example 755 of part C of table I; the cross-sectional area is 3.14 x 10-4 cm2;

Fig. 8 is a graph illustrating the release rate curve of the gap according to the invention and corresponds to Example 8 of part C of Table I; the cross-sectional area 60 is 3.14 × 10 −4 cm2. The test is carried out at 21 ° C and a relative humidity of 65%;

fig. 9 is a graph illustrating the curve of the rate of release of the groove, in accordance with the invention, and corresponds to example 9 of part C of table I; the cross-sectional area 65 is 3.14 × 10 -4 cm 2;

fig. 10 illustrates the variation of the release as a function of time in the case of frontaline disseminated by a tube open at both ends and corresponds to Example 3 of Part B of Table I; the tube with vertical arrangement has an internal diameter of 0.4 mm; the line segment in dashed lines corresponds to the empty tube;

fig. 11 is a curve of variation of the release as a function of time in the case of the frontaline disseminated in accordance with the invention and corresponds to Example 1 of Part C of Table I;

fig. 12 illustrates another embodiment of the invention in which, instead of using separate tubes, flat sheets are embossed to form channels (the rectangular channels are shown, but they can have other shapes and be for example semi-circular) and this sheet is made to adhere to a support sheet so as to obtain several parallel capillary tubes; the channels, in this figure, are shown empty and not closed;

fig. 13 illustrates transverse closure zones formed on parallel groups of channels of FIG. 12 after these channels have been filled with substance to be evaporated;

fig. 14 is another view of the device of FIG. 3, part of which is shown with the tubes fixed to a material such as an adhesive coated support strip, the tubes being heat sealed so that they are closed at regular intervals in the longitudinal direction;

fig. 15 is an end view, on a larger scale, of the device of FIG. 14, and fig. 16 is a sectional view along line 16-16 of FIG. 14.

In the accompanying drawings, similar references have been chosen to designate corresponding parts. The dimensions of some of the parts as shown in the drawings may have been changed and / or exaggerated to give clarity to the illustration and understanding of the present invention.

An advantageous embodiment of the invention resides in the use of hollow fibers as reservoirs and distributors for the vapors to be disseminated for various purposes (for example perfumes for artificial flowers), but in particular for the sexual pheromones of insects , when pheromones are used as bait, or to interrupt the natural mating processes of insects, by the so-called rupture technique. The pheromone deposited in the core of hollow filaments of suitable length and internal diameter is released by evaporation at one end of a small tube, the other end of which is closed.

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The hollow filaments of the invention can be made from any of various natural or synthetic polymeric materials by any of the methods commonly used in the production of artificial fibers. Materials to be used are polyesters, polyolefins, acrylic polymeric materials and polyamides.

In fig. 1 of the accompanying drawings, a capillary tubular filament 2 according to the invention, having a lumen 4, is closed at one end by heat welding or by means of a plug 6, for example a cement based on epoxy resin or another suitable material, and it is charged with the attractant 8 acting on insects. The attractant 8 preferably forms a meniscus 10 of the wetting type at its open or upper end, relative to the material of the tube. If such a meniscus is not obtained between the vaporizable material and the tube, the suitable material of constitution of the tube is then chosen for a given vaporizable material.

Fig. 2 represents a group 12 of tubes 2 which are held together by conventional means (not shown) for example by an external bandage or by bonding to each other or by placing in a suitable external container. The open ends of the tubes are located at the top and the bases of the tubes are conventionally fixed on a support or base 14. The total amount released of insect attractant or floral scent, when the invention is used to generate a scent for artificial flowers, depends,

as indicated above and below, the diameter of the tubes, the particular material used and the number of tubes forming the group 12. Since there is an immense number of possible variations of these factors, it is impossible to list all combinations, but this is not necessary for the understanding and application of the invention. Those skilled in the art can readily assemble the required number of tubes once the rate of release of a given tube containing a given material has been determined. As shown in part C of Table I for certain attractants chosen by way of example, the release rate is easy to determine. Consequently, it is sufficient, in order to design a disseminator for a given total quantity of material, to know the duration in hours of the desired release and the weight of attractant necessary for this number of hours; the amount of attractant per tube is determined by simple calculation, and the number of these tubes that must be assembled to form a group 12 can then be easily calculated (i.e. by dividing the total amount of attractant by the quantity attractant per tube).

Figs. 3a and 3b show another embodiment of the invention in which a group of capillary tubes like the tubes 2 adhere to a support strip, fixed from place to place in the longitudinal direction and wound in a form facilitating distribution, as indicated in 15. The attractant 8 does not escape from the tubes before the latter have been sectioned at selected locations between the closed regions. Other details of this embodiment are shown in FIGS. 14, 15 and 16.

The two embodiments described above illustrate two methods of mounting the tubes and the groupings of the tubes can be large or small depending on the particular needs. In practice, several of the assemblies in FIG. 2 or fig. 3a and 3b can be arranged in a growing area which it is desired to protect from insects, so that, whatever the wind direction, the insects are attracted at least to some of the sites. In general, these embodiments are used in conjunction with insect traps for the control of parasite populations or their elimination by direct trapping. Fig. 4 illustrates another embodiment in which individual filled fibers are welded and sectioned so as to expose one or two closed channels at one end. These individual fibers can be spread on crops or land by suitable land or airborne distributors and can be used for the process of applying pheromones by rupture.

Fig. 5 shows a characteristic release rate curve (the weight losses are plotted on the ordinate and the times are plotted on the abscissa) of the carbon tetrachloride which is used by way of example to establish a reference release rate. It is noted that, at the very beginning, the weight loss is relatively strong, as indicated by the portion of the curve A which decreases very quickly shortly after the start of the release. The curve then flattens out and becomes almost horizontal, as indicated by portion B. It is this low rate of prolonged release which constitutes one of the most important advantages of the invention. The exact shape of the curve varies slightly depending on the material used and the diameter of the tubes, but in general it can be said that the curves of all the tested materials fall into the same class of curves.

Figs. 6, 7, 8 and 9 represent respective curves of application of the invention to o-dichlorobenzene, linalool, disparlure and grandlure. The compositions of these substances or their chemical names are as follows:

linalool: terpene alcohol disappeared: cis-7,8-epoxy-2-methyloctadecane grandlure: mixture of the following components:

a) cis-2-isopropenyl-1-methylcyclobutylethanol b) cis-3,3-dimethylcyclohexylidene-ethanol c) cis-3,3-dimethylcyclohexylidene-acetaldehyde d) trans-3,3-dimethylcyclohexylidene-acetaldehyde. When the controlled release of more than one individual substance is desired, it is possible to use bundles or groups of individual fibers loaded with different volatile substances. By the appropriate choice of the diameters of the individual fibers or of the relative numbers of fibers loaded with different materials, mixtures of vapors of controlled composition can be disseminated. Examples of this variant include: 1) the combined use of attractants and toxic substances, 2) the use of attractants which are chemical mixtures or which require a synergistic chemical agent in precise proportions to be effective, and 3) perfumes or air fresheners that require a mixture of chemicals to produce an optimal effect.

This variant is particularly useful when mixtures of chemicals with substantially different volatilities have to be dispensed to produce a mixture of vapors of fairly constant composition. The appropriate choice of fiber lengths, as well as their diameter or number, makes it possible to compensate for the differences in evaporation rates, thereby delivering a mixture of vapors of controlled and constant composition. This variant is also advantageous when the materials which it is desired to release simultaneously at a regulated speed are incompatible with each other (that is to say immiscible or chemically reactive in the condensed phase).

As indicated above, the reason for providing tubes of different diameters is that the variation in the diameters of the tubes is one of the factors which affect the rate of evaporation or the rate of release of the attractant. Instead of using tubes of different diameters, a variant consists in using tubes of the same diameter, but the tubes filled with one material are more numerous than the tubes filled with another material, the ratio of the numbers of tubes determining the ratio resulting from the compounds in the vapor state. If, for example, in a vapor dispersion of two compounds, it is desired that there are three parts of one compound for one part of the other compound as the vapors mix out of the ends of the tubes, a bundle of tubes of the same predetermined diameter must comprise three times as many tubes of one compound as there are tubes of the other compound, which gives the desired mixture of compounds. Naturally, to obtain a vapor which is a mixture, the evaporation rates of the vaporizable materials

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individual factors should be considered as factors, and evaporation rates can be advantageously used along with tube diameters or ratios of tubes of one material to tubes of other materials, to obtain the desired vapor. The combinations of these variables are almost infinite in number and, therefore, a detailed description will not be given. It is possible, by this technique and in accordance with the invention, to produce vapors containing several well defined compounds. In actual practice, the manufacturer of the device could pre-load tubes of various materials; then, on the basis of an order from its customers, the required number of tubes would be assembled in accordance with the wishes of the purchaser with regard to the relative proportions of the components of the vapor released. In assembling the bundles of tubes, it would naturally be necessary to consider the weight loss curves corresponding to the various compounds.

For example, if the buyer wants an attractant in combination with an insecticide, the vapor of which is the destructive factor, he must order tubes, some of which constitute the bundle would contain the attractant, while the others would contain the liquid insecticide. Vapors mix as they exit tubes, producing a mixture of the desired amount of insecticide and attractant. The attractant would attract the insects to the installation site of the bundled tubes and the insecticide would kill the insects when the latter entered the vapor zone.

Fig. 10 is a curve of variation of the release rate as a function of time in the case of the dissemination of frontaline in accordance with the previous methods, from a microscopic tube made of 0.4 mm polyethylene terephthalate, this curve corresponding to the data from line 3 of part B of table I. It illustrates the high constant speed which characterizes this process.

Fig. 11 illustrates the dissemination of the same pheromone from the same tube as that used in FIG. 10, except for the details defined in accordance with the invention. It clearly shows the much lower set speed that is obtained after the initial large drop in speed, as described in the previous examples according to the invention (it should be noted that, in FIG. 11, the values plotted on the abscissa are in g / hx 105 while in Fig. 10 they are in g / min x 105).

Fig. 12 shows an embodiment in which the capillary tubes result from the prior shaping of a sheet designated as a whole by 40 so that it has the channels 42. These channels are represented five in number, but we can use any number desired. Likewise, the channels 42 are shown as having a rectangular cross section, but one could also use semicircular, oval or other polygonal shape channels. It should be noted that the bases of the channels are open and that the sheet 40 is fixed by means of conventional adhesives to a base sheet 44 by securely fixing the portions 46 to the sheet 44. As a result, capillary tubes 48 of predetermined section and dimensions are formed between the support sheet 44 and the channels 42.

Fig. 13 illustrates the channel system of the composite sheet of FIG. 12, the channels being filled and sealed transversely, as indicated in 49.

Figs. 14, 15 and 16 show more details of the embodiment of the invention illustrated in FIGS. 3a and 3b. A strip 65 of suitable material is used, carrying a layer 66 of adhesive. This material may be a tape ordinarily used as a cover or wrapping, carrying a layer of pressure-sensitive adhesive. Several tubular filaments 68 extend along the adhesive tape 64 and adhere to this tape by means of the adhesive 66. If necessary, the adhesive 66 may be of the type that is covered before the use of a protective sheet removed by pulling but, in practice, when the sheet is removed and the tubes 68 adhere to it, the adhesive hardens in air in order to firmly fix the tubes 68 to the strip 64.

The tubes 68 can be placed on the strip 64 before or after their filling. After having been filled and when they are placed on the strip, they are heat sealed along the joining lines 70, the material which constitutes the tubes being such as to be able to be heat sealed by the application of 'a heat welding member. Under the effect of this heat welding, the wall of the tube collapses at points 70, thus forming for each elongated tube several sections 72, each being only a portion of the total length of the individual filaments. In practice, the user makes a cut transverse to the tubes so as to form short conduits of the desired length of tube, the cut being carried out between the portions 70 heat sealed. The length of the sections of tube from the closed end, heat sealed, to the open end, where the cutting is carried out, determines, all other parameters being considered in accordance with the teaching of the invention, the actual length of the individual section 72. The embodiment of FIGS. 14 to 16 is a practical form which makes it possible to provide a potential user with a roll or a flat section of filamentous tubes, already fixed on a support, but the tubes of which are sealed to prevent any loss of material until the tubes should be used. When the user wishes to use a certain portion, he cuts from one end of the material the corresponding length of tube (the cutting being carried out transversely to the width of the strip), so as to open the ends of the tubes. The length of tube it must cut depends, among other possible factors, on the number of hours of vapor emission by the cut section of the assembled tubes.

In the practice of the invention, the tubular fibers of polymer material reduced to the appropriate dimensions are loaded with an insect attractant by one of the methods described below. The dimensions of the hollow fibers, from a practical point of view, are generally between about 0.025 and 1.0 mm as regards the outside diameter, and between 0.01 and 0.8 mm as regards the inside diameter, although that it is obvious to the technician in fiber extrusion that microscopic tubes exceeding these limits in one direction or the other can be obtained and constitute variants of the invention. The dimensions illustrated therefore represent a preferred range rather than a limiting range. The length of the hollow fibers depends on the desired duration of release of the attractant. Thus, for a given attractant, the invention makes it possible to influence the speed of release by the number and the internal diameter of the fibers which are used and to influence the period of activity by the choice of the suitable length of fiber. . The release rate curves, showing how the release behaves in accordance with the invention, typically show a brief period of high speed release followed by a long period of roughly asymptotic behavior, where the decrease in release speed, as shown by the slope of the asymptotic portion of the curve, is so low that it approximately represents a linear release speed. These release rate curves are discussed below in connection with several of the examples of the invention in which the tests have been carried out successfully.

The invention is illustrated by the following examples.

Example 1:

This example corresponds to line III of part C of table I and illustrates the behavior of release or evaporation of carbon tetrachloride (compound chosen as reference for relatively volatile attractants or insecticides) from hollow fibers not stretched in polyethylene terephthalate. The fibers have an outside diameter of 0.254 mm and an inside diameter of 0.203 mm. Hollow fiber sections

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measuring 127 to 203.2 mm are loaded with carbon tetrachloride, closed at one end with epoxy resin cement and mounted in a vertical position, the open end facing upwards, on a flat surface. The internal cross-sectional area is approximately 3.245 x 10 −4 cm 2. The release of carbon tetrachloride from the interior of the fiber by evaporation and diffusion through the open end of this fiber is measured by following the shrinkage of the meniscus of liquid inside the fiber by means of a cathetometer. The increasing losses in volume are converted into losses in weight and their variation as a function of time is reproduced on the graph of Fig. 5. In this case, a quasi-linear release speed is observed after 30 h.

The release is measured at an almost constant rate of weight loss and the values given in the graph are the means of five tests each time.

Example 2:

The o-dichlorobenzene, chosen as a reference substance for attractants or insecticides of intermediate volatility, is loaded by capillary action into a hollow fiber of unstretched polyethylene terephthalate with an internal cross-sectional area of 3.09 × 10 "4 cm2. Filled hollow fibers, 127 mm in length, are sealed at one end with epoxy resin cement and are arranged vertically with the open end facing up on a surface The release of o-dichlorobenzene from the hollow fibers is observed and measured by following the shrinkage of the meniscus inside the fiber Fig. 6 graphically represents the curve obtained in this test, and corresponds to the data of the line 4 of part C of table I. The almost linear speed of release is obtained after approximately 90 h.

Example 3:

The data in this example correspond to row 7 of part C of table I. The terpene alcohol (linalool) chosen as a model for the groove, that is to say the attractive pheromone of the cotton weevil, is loaded into hollow fibers of unstretched polyethylene terephthalate with an interior cross-section of 3.14 x 10 ~ 4 cm2. Sections of loaded fibers from 102 to 127 mm, closed at one end with a cement, are mounted in a vertical position, the open end facing upwards, on a flat surface. The release of the linalool from the hollow fibers is monitored by following the removal of the meniscus inside the fiber using a cathetometer. Fig. 7 illustrates the release curve of the linalool. After about 40 h, the release speed takes a constant value of 5 x 10-9 g / min. If we assume a desired release speed, for a bait attracting the cotton weevil, of 3 x 10 "4 g / d and a required attraction period of 168 d, the calculation shows that the configuration of the bait requires 42 open fiber ends, the individual fiber sections measuring 3.8 cm.

Example 4:

This example corresponds to line 8 of Part C of Table I. The disparlure, which is the sexual attractant of disparate bombyx males, is loaded into hollow fiber of unstretched polyethylene terephthalate, the interior section area of which right measures 3.4 x 10 ~ 4 cm2. The disappearance release curve is plotted as shown in Example 1. The release rate becomes constant at the value of 1.44 x 10 -6 g / d / fiber end, as shown in release curve shown. in fig. 8. The desired deliberation speed for a bait consisting of a disparate bombix sex pheromone trap is 2.16 x 10 ~ 4 g / d and the desired period of activity is 90 d. Thus, a bait formed from a hollow fiber trap would require three open fiber ends and an individual fiber length of 0.46 cm per open end.

A commercial insect trap filled with a tacky substance to hold butterflies attracted to the trap was primed with dissolving hollow fibers and placed in a wooded area of Norfolk County, Massachusetts, during the month of August 1974 The pheromone primed trap captured the disparate bombyx males in a ratio of 3: 1 compared to an unbaited trap.

Example 5:

This example corresponds to line 9 of part C of Table I. The large size, that is to say the pheromone exerting an attraction on the cotton weevil, was loaded into a hollow fiber in unstretched polyethylene terephthalate having an interior area of straight section of 4.14 x 10 ~ 4 cm2. The release curve of the large size was plotted as described in Example 2. The release rate became constant at a value of 5 × 10 -9 g / d / fiber end, as indicated by the release curve shown in Fig. 9. The desired rate of release for a pheromone primer from the cotton weevil is 3 x 10 "4 g / d and the desired period of activity is 168 d. Thus, a hollow fiber trapping primer would require 40 open fiber ends with individual fiber lengths of about 4 cm per open end.

The hollow filaments of the invention can be loaded in various ways with attractive substances. The liquid composition of the attractant fills the hollow filament by capillary action or by gravity using the filament as a siphon. (In the siphoning method, one end of one or more tubes is immersed in the desired liquid. The other ends of the tubes are below the liquid level. A slight suction is exerted on the lower ends. When the liquid has started to flow, the siphoning action continues and the tubes fill up.) Another filling process involves simply sucking the liquid into the fiber core by arranging the ends of the fibers below the liquid level and depression of the other end using a suction bulb or a water pump. Another method involves placing fiber segments below the liquid level and compressing them to expel the air, after which they are contracted to expel the liquid. It is also possible to fill the fiber during spinning by injecting the liquid formulation of attractant as liquid forming the core during the spinning operation. Other methods of filling the capillary filament can be imagined, but it should be noted that the particular method of filling does not come within the scope of the invention.

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Claims (9)

615 806 1. Device for the dissemination of a vaporizable substance at a predetermined speed by diffusion of the vapor through a layer of stagnant gas, characterized in that it comprises at least one elongated conduit (2) containing the substance vaporizable (8) which is closed at one end and which is constituted by a material chosen from polyesters, polyolefins, acrylic polymers and polyamides, and the layer of stagnant gas covers the vaporizable substance in the conduit. 2. Device according to claim 1, characterized in that the conduit (2) is a capillary tube. 2 3. Device according to claim 1 or claim 2, characterized in that the duct has a sealed area between two open ends and a vaporizable substance in the portions thus defined. 4. Device according to one of claims 1, 2 or 3, characterized in that it comprises several elongated conduits. 5. Device according to claim 4, characterized in that the conduits have at least two different predetermined cross-sectional areas. 6. Device according to claim 4 or 5, characterized in that the conduits are formed by blocked channels formed in a sheet material. 7. Use of the device according to claim, for combating insects, characterized in that at least one tube contains a vaporizable insecticide. 8. Use of the device according to claim 7, characterized in that the insecticide is mixed with a product which exerts an attraction on insects. 9. Use of the device comprising several conduits according to claim 7, characterized in that some conduits contain insecticide and others a product exerting an attraction on insects.